#14880: GHC panic: updateRole -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler (Type | Version: 8.2.2 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: #15076 | Differential Rev(s): Phab:D4769 Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Wow! It never occurred to me that the incidental change around ordering (which was entirely unforced -- done just so that users would more often see variables reported in an order similar to what was written) could have such an impact on performance. I suppose it's because `mapUnionFV` can get inlined but `f` can't? Happily, the solution is dead simple: just don't make that change! (We still can, I imagine, make the changes in UniqDFM. I'd be even more flabbergasted if those changes affected performance.) Thanks! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14880#comment:116 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler